feat: persist voice samples to disk, generate VTT, cleanup after analysis

internal/infrastructure/speech/audio_converter.go

@@ -26,6 +26,9 @@ func NewFFmpegConverter(ffmpegPath, tempDir string) *FFmpegConverter {
 	return &FFmpegConverter{ffmpegPath: ffmpegPath, tempDir: tempDir}
 }
 
+// Convert converts audio bytes between formats and returns the converted bytes.
+// Intermediate temp files are cleaned up automatically — use ConvertFile when
+// you need to keep the output on disk.
 func (c *FFmpegConverter) Convert(ctx context.Context, input []byte, fromMime, toMime string) ([]byte, error) {
 	id := uuid.New().String()
 	inFile := filepath.Join(c.tempDir, id+".input")
@@ -38,6 +41,32 @@ func (c *FFmpegConverter) Convert(ctx context.Context, input []byte, fromMime, t
 		return nil, fmt.Errorf("write temp input: %w", err)
 	}
 
+	if err := c.runFFmpeg(ctx, inFile, outFile); err != nil {
+		return nil, err
+	}
+
+	out, err := os.ReadFile(outFile)
+	if err != nil {
+		return nil, fmt.Errorf("read converted file: %w", err)
+	}
+	return out, nil
+}
+
+// ConvertFile converts audio bytes and writes the WAV output to outPath.
+// The caller is responsible for deleting outPath when no longer needed.
+func (c *FFmpegConverter) ConvertFile(ctx context.Context, input []byte, outPath string) error {
+	id := uuid.New().String()
+	inFile := filepath.Join(c.tempDir, id+".input")
+
+	defer os.Remove(inFile)
+
+	if err := os.WriteFile(inFile, input, 0600); err != nil {
+		return fmt.Errorf("write temp input: %w", err)
+	}
+	return c.runFFmpeg(ctx, inFile, outPath)
+}
+
+func (c *FFmpegConverter) runFFmpeg(ctx context.Context, inFile, outFile string) error {
 	cmd := exec.CommandContext(ctx, c.ffmpegPath,
 		"-i", inFile,
 		"-ar", "16000",
@@ -46,18 +75,10 @@ func (c *FFmpegConverter) Convert(ctx context.Context, input []byte, fromMime, t
 		"-y",
 		outFile,
 	)
-
 	var stderr bytes.Buffer
 	cmd.Stderr = &stderr
-
 	if err := cmd.Run(); err != nil {
-		return nil, fmt.Errorf("ffmpeg conversion: %w: %s", err, stderr.String())
+		return fmt.Errorf("ffmpeg conversion: %w: %s", err, stderr.String())
 	}
-
-	out, err := os.ReadFile(outFile)
-	if err != nil {
-		return nil, fmt.Errorf("read converted file: %w", err)
-	}
-
-	return out, nil
+	return nil
 }